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NatureInterface > No.01 > P070-074 [Japanese]

Development of Fuel Cells and Prospects for Bringing about a Distributed

図の英語はありません。

Development of fuel cells and prospects for bringing about a "distributed energy society"

-The biggest contribution of fuel cells is the creation of an "energy democracy"

Manabu Akaike

President, Universal Design Intelligence, Inc.

A "fuel cell hybrid system" leads to the future of energy

"Renewable and sustainable energy will be used with higher priority without changing the balance in nature. The consumption of non-reusable energy will be reduced as much as possible by limiting and prioritizing its use. Meanwhile, energy efficiency will be enhanced using methods such as re-powering, and non-reusable energy will be replaced aggressively with reusable energy."

Next-generation energy has been discussed among many, including numerous experts. The conclusions, however, are already given in the principle described in the above paragraph.

It is obvious that achieving sustainable energy means using "natural energy" effectively. There are already energy resources that serve as alternatives to fossil fuels: wind power, solar power, terrestrial heat (geothermal energy) and tidal/wave power. An electric power supply that is to some extent independent of fossil fuels should be possible if we make use of distributed natural energy sources by taking advantage of regional climate characteristics. However, it is true that there are many challenges in the effective use of natural energy resources. The biggest challenge is that the natural energy resources are not suitable for large-scale power generation. Another apparent barrier for using these natural resources is that their cost is too high at present.

On the other hand, there are more problems in depending on non-sustainable energy resources, as is symbolically shown in the Japanese government's plan to build another twenty nuclear power plants. The safety concerns surrounding nuclear power generation are still unsettled. Furthermore, two thirds of the generated heat is wasted by being released into the environment, and this causes adverse effects on a region's ecology. Nuclear power's inefficiency in its simultaneous electric and thermal transmission is obvious.

As we have discussed above, neither scenario--replacing fossil fuels with natural energy resources or increasing the number of nuclear power plants--could solve all energy problems. What is needed now is nothing other than to design a new energy system by intelligently combining the available resources, and to explore and establish a third scenario.

With such a background, the idea of a "sustainable distributed energy system based on fuel cells" has emerged. In this new power generation system, which creates electric power from oxygen and hydrogen separated by a membrane, no waste, such as CO2, is produced. The fuel is available flexibly from material choices, including biomass. A wide range of applications, including home appliance power supply, home power generation, intelligent building power supply and regional distributed power generation, will be possible by controlling the number of electrolyte units.

The most important thing is that the "fuel cell hybrid," which is the combination of various energy sources such as solar, wind and garbage power generation, heat pump and micro-cogeneration, will create a distributed energy society by using the fuel cells as a bridge.

"PEM-type fuel cell research" creates the future

Quite a few automotive manufacturers are competing to develop a type of fuel cell called a "proton exchange membrane" (PEM). This fuel cell consists of a solid electrolyte membrane coated with platinum catalysis and an electrode that permeates gases. The membrane is sealed using bipolar plates. The membrane at the center is a polymer film 0.2~0.3 mm thick. This polymer film permeates only protons (hydrogen ions). At the cathode, electrons are emitted because hydrogen atoms are ionized. At the anode, on the other hand, oxygen molecules from the air are reduced and react with hydrogen ions to form water. The basic power generation mechanism is that electric current is created between the cathode and anode using the potential difference.

This fuel cell system, which generates electric energy by having hydrogen and oxygen react, discharges only water as waste and creates heat. Currently, Daimler-Chrysler and BMW in Germany, Toyota, Honda and Mazda in Japan and other companies are developing this type of alternative energy because it has the potential to achieve low emission and efficient cogeneration, namely the use of both the electricity and the heat. Furthermore, unlike conventional power generation technologies that include mechatronics such as turbines, this fuel cell works purely on a biochemical level. This fuel cell has been expected as an environmentally acceptable, quiet and clean power generation system.

It is commonly known that hydrogen can be produced from a variety of materials, thanks to the progress in ferment technologies and catalysis technologies. A rapid cost reduction is well expected if the fuel cells are mass-produced by precision press fabrication technologies for use in automobiles. A "An economy of scale" based on mass production may be possible immediately if the fuel cells become small enough and light enough, and if a wide range of applications become visible, including home appliances and distributed power supplies in buildings. In short, the ultimate goal of a cogeneration system built around fuel cells is to use such a system not only in automobiles but also in homes and throughout regions.

Fuel cells for business use evolve into a home power supply

Besides the advantage that fuel cells are clean, they are also suitable for Japan's energy strategies to prevent global warming, because they are good for securing energy that is in high demand in Japan. It means a lot for Japan, which depends highly on imported energy resources, that the cell fuels--hydrogen and methanol--can be produced from natural gas that is buried in Russia in immense amounts, and that these gases can also be produced from various materials including plants.

The fuel cell system may also develop into a mainstay energy generation system. Since the amount of power generated is flexible, the system can be used in a wide range of applications, from large-scale power generation, which electric companies have conventionally carried out for communities and companies, to power generation in places like hotels, hospitals and homes.

According to estimates by Kansai Novel Technology Laboratory, each home can save 73,000 yen a year if a fuel cell system using city gas as the fuel is used, assuming a power capacity of 0.3 kW, an equipment cost of 300,000 yen and a gas cost of 1,300 yen/hour. The equipment cost is thus paid back in 3.7 years. Self-sustaining electricity will account for 59.6% of the total, and self-sustaining heat 22.9% of the total.

Fuel cell systems have an advantage in both hotels and hospitals, where electricity 24 hours a day is essential. Take a hotel with 2000 m2 floor area as an example. The cost payback time is 7.8 years if this hotel installs a 15 kW PEM fuel cell system assuming a gas price of 80 yen/hour. This economical evaluation will be much better if the system price is reduced to about 200,000 yen/kW.

Thus far, fuel cell generation is in use at 60 sites in Japan and only 26,000 kW has been generated. However, many other places seem to be about to start using the system.

Asahi Beer Corporation has installed a 200 kW phosphoric acid type fuel cell system in its Shikoku brewery in Ehime prefecture. Sapporo Beer Corporation has installed a fuel cell system of about the same capacity in its Chiba brewery. The company plans to cover 6% of that brewery's electricity needs by utilizing the methane gas created in gas-rejecting type water-waste processing facilities. The investment was 230 million yen, but the savings are expected to be 30 million yen per year. The fuel system is a phosphoric acid type, which creates hot water. The hydrogen fuel can be obtained by adding steam to high-temperature city-supplied gas.

Sanyo Electric Corporation has also developed a cogeneration system for stores and houses using the same type of PEM fuel cells. This system generates electricity using the natural gas supplied to each home, while the heat is sent to secondary uses, such as air conditioning and water heating. The system has been developed in the form of small equipment combining with an air conditioner for the purpose of reducing household use of electric power.

The company entered the business by being the first to commercialize a portable power supply for emergency use and use at construction sites. It plans to extend the technology to simultaneous heat and electricity supply. Electricity is produced first using the oxygen in the air and the hydrogen taken from natural gas. The heat produced in the steam is used as a heat source for an air conditioner and a hot-water supply system. In the case of using the heat in the air conditioner, the generated electricity is used in the compressor to cool the air, and the heat can be used in warming. The company estimates that the maximum power is 50 kW and the energy efficiency for the heat and electricity combined is 35%. Significant energy savings will be expected if such a system becomes widely used.

Research and development of fuel cell technologies promoted by collaboration among industry, government and universities

For the fuel cells to penetrate into homes and automobiles as a distributed generation system, further scaling down of the equipment is necessary. A few problems that the fuel cell has, along with its advantages, must be overcome to accomplish this.

The biggest advantage of the fuel cell is that it can be small and yet generate power with high efficiency. Generally the efficiency is higher when the cell is operated at low current, because voltage loss increases as the current increases. This means that the fuel cells are more efficiently used in a distributed small system than in large-scale power generation facilities. However, although the theoretical power generation efficiency is higher at low temperatures, the speed of the cell reaction is slower and the electric resistance of the electrolyte is high at low temperatures. For this reason, it is necessary to develop higher performance cell catalysis and high conductance electrolyte.

As mentioned earlier, the total energy efficiency can be enhanced in the fuel cell system because the heat byproduct can be utilized. In the PEM-type fuel cells, the temperature is about 50 ℃. For use in houses, a higher temperature, about 90 ℃, is preferable. This is another hurdle that must be cleared.

There is another problem on the fuel side. To use hydrogen, a fuel supply infrastructure must be prepared. It is still a problem that carrying the fuel is very difficult. When we are to obtain hydrogen from methanol, the methanol must have a very high purity. Therefore, development of conversion technologies is necessary, including a CO intoxication prevention method and a way to scale down the converter size.

The development of fuel cell technologies is, nonetheless, progressing rapidly now. Not only the membrane technology, which is a core technology of fuel cells, but the technologies related to direct-drive motors, regenerative brakes, controllers and optical fiber cables are requested in various ways. These technologies have been accumulated in small to medium-sized venture companies and manufacturers other than automobile makers. If fuel cells will become commercially viable when they penetrate into homes, the cost should be reduced further due to economies of scale.

Ballade Corporation in Canada, a venture company specializing in the PEM-type fuel cells, has already developed a portable radio cassette player and a cellular phone using ultra-small fuel cells. There are prospects for fuel cell applications in back-up power supply, in case of natural disasters, and in notebook and handheld computers. Another possible application, when much smaller fuel cells are developed in the near future, is as a heart-pacemaker power supply that takes advantage of the fact that the only waste from the fuel cell is water.

Some fuel-related technologies, such as hydrogen storage using compressed hydrogen, hydrogen adsorption to carbon nano-tubes and hydrogen storage in metal composites, are becoming practical. The Japanese gas suppliers have the technologies to produce hydrogen from natural gas, with which they have dealt for many years. In the near future, a new system should certainly emerge that supplies pure hydrogen from natural gas stored in a fuel station to the hydrogen-producing equipment and finally to automobiles.

Recently, a research team at Hokkaido University disclosed a new catalysis method that can produce hydrogen and benzene from cyclohexane at low cost. Cyclohexane is a stable liquid material at room temperature and consists of hydrogen and benzene. The feasibility of using such an easy-to-handle material has been demonstrated. From now on, research into the use of such a chemical halide material, as well as easy-to-use fuel for fuel cells in conjunction with the catalysis technologies, should become big challenges in the fuel cell business.

In the future, the active use of methanol as the fuel for fuel cells should mean a lot. Currently methanol is mainly produced from natural gas, but it can also be produced from various kinds of biomass such as agricultural products, grass, trees and seaweeds, all of which can be regenerated. Methanol can also be retrieved from wastes like used paper and felled trees. If methanol is produced from biomass, it will be a perfect recycling energy system because the amount of CO2 emission at methanol creation equals the amount the plant had absorbed before.

As we have discussed, the PEM-type fuel cell energy system is promising as a distributed power generation system in a country that lacks natural resources. The use of biomass contributes to society by securing and protecting the land resulting from sustainable forest management practices, and by creating employment opportunities in those regions.

Studies into the effective uses of fuel cells as community systems are encouraged

To bring such a scenario into reality, we need to follow a few steps.

The first step is a "distributed power generation strategy using the fuel cell nucleus." To achieve this energy revolution, we must go through a big transformation from the current massively centralized, transmission-type power generation system to a small, distributed and independent system. Now is the time to start discussing the possibilities of micro-cogeneration and the ways to spread the distributed power generation society based on it.

From the viewpoint of construction facilities, research into the introduction of micro-cogeneration in homes before fuel cells is important. Such study must accelerate the improvement of gas turbine efficiency, and a house with a rotating engine will become one of the options. It is expected that this construction business will study comprehensively the use of such a system as well as the fuel cells.

Earlier in this article, it was mentioned that the low heat temperature was a problem to be overcome. Some types of fuel cells are different from the PEM type, which uses a solid-state polymer membrane. Solid-state oxide-type fuel cells have not got much attention as a power supply for houses because their operating temperature is very high, about 1000 ℃. But it does have potential if it's considered as a community power supply for multiple houses.

In next-generation housing, which is a goal in the construction facilities business, the use of community-level system technologies, such as shared purifiers and medium-scale water services, will probably be necessary. Feasibility studies of fuel cells should be a necessary component of construction policy making.

The second step is an "energy-intelligent strategy." Today, the reduction of traffic jams has been discussed by optimizing transportation logistics using ITS, for intelligent transport system. In the same context, an intelligent energy system in which demand and supply are optimized is wanted in next-generation regional management, corporate management and construction policies. The technology to supply the right amount of energy to the right places is necessary to achieve efficient management and house management. If there is surplus energy in distributed power generation, it can be sold to the energy supply companies. An optimum logistics system to do so must be established.

Next-generation intelligent housing has been discussed with excitement in the construction facilities business. It is surely desirable to study the use of conventional power supply, solar power generation and a "home energy information control system" that utilizes fuel cell energy efficiently.

It is obvious that in the next generation, we must materialize new designs along with the information revolution. According to NTT's analysis, in 2010 we will consume three times the energy we consumed in 1990, if the information revolution continues to develop at its current pace. It seems a total power design foreseeing the multimedia era will determine the destiny of the construction facilities business. Such a design must consider the power supply development for corporate use combining the fuel cells and solar power generation intelligently, structural change in network systems that allows low power consumption and switching to various low-energy-consumption type power equipment using advanced technologies.

"Energy democracy" achieved by fuel cells

The spread of cogeneration systems using fuel cells, which will be introduced after the above-mentioned steps are accomplished, will surely offer more options for people's convenience. The energy supply in regions and homes will change drastically when the cogeneration systems spread not only to stores but to apartment buildings and ordinary houses. If the current energy system changes, houses will change as a result. However, contrary to its spread in stores, good examples of cogeneration spreading over whole regions are very few. We cannot deny that complicated laws and regulation from government ministries suppress its spread.

There may be an opinion that investment in development and deregulation might discourage people's efforts to save energy, efforts that are indispensable if global warming is to be curtailed. It is true that global warming may actually accelerate if people's energy-saving intentions are discouraged because energy becomes conveniently and cheaply supplied. To prevent this, we should consider introducing an "environment tax" that encourages energy saving simply by making energy more expensive.

What can be said for sure is that a distributed power generation society will let people know the actual amount of energy they are using, information that has not yet been available to them. If how much fuel people are using is visible instantly, they will become conscious of the concept of energy self-supply and will therefore control their use of energy on their own. In short, the greatest significance of fuel cells is the materialization of the "energy democracy."

We have taken for granted that electricity is always available by inserting a plug in a socket, and that gas for our stove is always there when we turn the switch. We have had no doubt about it.

I believe that the biggest significance of the distributed power generation society based on in-house power generation will be that it will let people know such negligence and the sinful waste it resulted in.

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